Erythritol has attracted public attention as a low caloric sweetener having a sweetness of about 0.8 times as much as sucrose. A conventional method for producing erythritol comprises culturing an erythritol-producing microorganism in an aqueous medium containing glucose which is employed as a raw material. After removing cells, culture broth containing the erythritol, thus produced, is purified and the erythritol is crystallized, followed by collecting the erythritol crystals. In usual, the erythritol crystals thus collected should be dried to a low moisture content of 0.15% by weight or below. Since erythritol has a high melting point at 119.degree. C. and a good thermal stability, erythritol crystals are usually hot air-dried so as to achieve a high drying efficiency.
However the conventional method for drying erythritol crystals is disadvantageous in that an extremely long period of time is needed for reducing the moisture content to a desired level and that some portion of the crystals would cohere together during the course of drying and thus the crystalline properties and form are deteriorated. These problems are particularly serious in the case where the erythritol crystals have large particle size of from 500 to 700 .mu.m.
Under these circumstances, the present invention aims at providing a method for efficiently drying erythritol crystals to give a moisture content of 0.15% by weight or below, without deteriorating the crystalline properties and form.
In order to achieve the above-mentioned object, the present inventors have conducted extensive studies. As a result, they have successfully found out that erythritol crystals, even having a large particle size, can be dried to give a moisture content of a desired level without causing any cohesion of the crystals by fluidized drying said crystals with the use of a gas of a temperature controlled to a specific level.